My android display indicates I am connected when I am using WiFi but not USB and the USB symbol does not appear in the bar. After it shows connection the synchronization attempt starts but fails. The android device driver is installed on my PC and the USB symbol Even though in WiFi I am shown as connected to the host, I cannot synchronize my Thunderbird 52.5.0 calendar (Home). I want to synchronize only my calendar and not contacts. I am a little confused as BirdieSync calls it events and not calendar. Does this mean the same thing.

A calendar contains events. So it's possible to use both terms and synchronize events or calendars.

If you connect via Wi-Fi to BirdieSync server, you don't need Android USB driver. It is only needed if you want to connect via USB (in which case you also need to enabled USB Debugging in Android Settings).

If you succeed in connecting your Android device to BirdieSync server via Wi-Fi, but synchronization fails, then I would need the logs to investigate on the reasons of this failure.

Once your Android device is connected to BirdieSync server on the PC (this is important to be able to retrieve Android logs), could you please build a log archive with BirdieSync menu "Help/Archive logs..." and send BirdieSyncLog.zip to support(at)birdiesync.com ?